This collection contains subsamples of aquatic microalgae preserved in either glutaraldehyde or a high-iodine Lugol'ss solution (NEON sample class: ptx_taxonomy_in.preserved). Periphyton, seston, and phytoplankton samples are collected three times per year at wadeable stream, river, and lake sites during aquatic biology bout windows, roughly in spring, summer, and fall. Samples are collected using the most approriate sampler for the habitat and substratum type, including rock scrubs, grab samples, and epiphyton. In wadeable streams, periphyton samples are collected in the two most dominant benthic habitat types (e.g. riffles, runs, pools, step pools), and seston samples are collected from the water column near the S2 sensor. In lakes, water-column phytoplankton samples are collected near the buoy, inlet, and outlet sensors using a Kemmerer sampler, and in littoral areas using the best benthic sampling method for the substratum type. In rivers, phytoplankton samples are collected near the buoy and two other deep-water locations using a Kemmerer sampler, and in littoral areas using the most benthic sampling method for the substratum type. All field-collected samples are split into subsamples in the domain support facility, which are either processed in the facility (ash-free dry mass) or preserved and shipped to a contracting taxonomy laboratory. All samples are archived in 20 mL glass scintillation vials and stored in a temperature (17-18°C) and humidity controlled environment. Phytoplankton and seston samples are preserved in a 2% high-iodine Lugol'ss solution. Periphyton samples are preserved in 0.5% glutaraldehyde. See related links below for protocols and NEON related data products.